M1: 6:30 - the early AM cutoff time, for formula reference
A2: 21:20
B2: 7:45
C2: =IF(A2>B2, (1-A2), "")
D2: =IF(C2<>"", C2*24, "")
E2: =IF(A2>B2, MIN($M$1,B2), IF(A2<$M$1, $M$1-A2, ""))
F2: =IF(E2 <> "", E2*24, "")
G2: =IF(A2>B2, IF(B2>$M$1, B2-$M$1, ""), IF(A2<$M$1, IF(B2>$M$1, B2-$M$1, ""), B2-A2))
H2: =IF(G2<>"", G2*24, "")